1. Technical Field
This invention relates generally to percussive rotational impact hammers, and more particularly, to a percussive rotational impact hammer assembly for creating high peak torque for use in rotating a drill bit in a downhole hammer, in a wrench for loosening and tightening threaded fasteners, or in other mechanical devices where high torque is required.
2. Background Art
Rear, U.S. Pat. No. 4,932,483 discloses a downhole hammer connected to a rotatable drill string. The hammer comprises a top sub and a drill bit support separated by a tubular housing incorporating a piston chamber there between. A feed tube is mounted to the top sub and extends into the piston chamber. A piston is slidably received in the housing and over the feed tube. Fluid porting is provided in the feed tube and the piston to sequentially admit fluid in a first space between the piston and top sub to drive the piston towards the drill bit support and to a second space between the piston and the drill bit support to drive the piston towards the top sub. Rotary motion is provided to the hammer assembly and drill bit by the attached drill string powered by a rotary table typically mounted on the rig platform. A shortcoming of this design is that the whole drill string has to rotate, rather than only the bit, making it difficult to drill directional holes with, for example, coiled tubing.
Johns, et al, U.S. Pat. No. 5,305,837 discloses another downhole air percussion hammer suited for directional drilling. The air compression hammer mechanism comprises a piston that reciprocates while simultaneously rotating in its housing. A hammer drill bit slidably keyed to the bottom of the piston transfers the impact energy to the formation and rotates during operation independent of an attached drill string. The kinetic energy of the reciprocating piston is employed to rotate the bit. The linear motion of the piston is converted into rotational motion by using one or more helical grooves formed by the piston body. To prevent the piston from oscillating in the rotary mode, an indexing clutch mechanism is provided to induce bit rotation in one direction only. A shortcoming of this design is that very high damaging forces are created in the helical grooves, which adversely affects the life of the hammer.
The present invention is distinguished over the prior art in general, and these patents in particular by a percussive rotational impact hammer assembly for creating high torques wherein a generally cylindrical piston rotatably mounted on a hammer inside an outer casing oscillates on the hammer and strikes an impact surface on the hammer. The interior surface of the outer casing and exterior of the hammer form an annulus in which the piston rotatably oscillates and the piston divides the annulus into an impact-driving chamber and return chamber. The piston and hammer have pressurized fluid ports and passageways for conducting pressurized fluid to alternately pressurize the chambers to rotate the piston such that an impact face on the piston strikes an impact face on the hammer and the kinetic energy of the piston and the rotational movement is transmitted via the hammer to a member engaged with hammer, such as a drill bit or other member. The rotational impact hammer assembly can be adapted for use in a downhole hammer, in break out tongs for drill pipe, in wrenches for loosening or tightening nuts and bolts, or in other mechanical devices where high torque is desired. Another aspect of the invention is a downhole percussive hammer/drilling tool incorporating the rotational impact hammer assembly. Still another aspect of the invention is a wrench incorporating the rotational impact hammer assembly for loosening or tightening nuts and bolts or other threaded connections.
It is therefore an object of the present invention to provide a percussive rotational impact hammer assembly that can create significantly higher peak torque than conventional air hammers.
It is another object of this invention to provide a percussive rotational impact hammer assembly which can be easily adapted for use in a downhole hammer, in break out tongs for drill pipe, in wrenches for loosening or tightening nuts and bolts, or in other mechanical devices where high torque is needed.
Another object of this invention is to provide a downhole percussive rotational impact hammer having a hammer member that engages with a drilling bit by means of splines, polygon shape or similar engagement surface as the bit works in a borehole.
Another object of this invention is to provide a percussive rotational impact hammer assembly having a hammer member sized and shaped to be received in a cylindrical outer casing having a cylindrical interior surface to define an annulus between an outer cylindrical sliding surface of the hammer member and the interior surface of the outer casing in which a piston member rotatably oscillates to transmit kinetic energy and rotational movement in one direction to a member engaged with the hammer.
A further object of this invention is to provide a percussive rotational impact hammer assembly having a piston member rotatably mounted concentrically on a sliding surface of a hammer member and having an arcuate sidewall portion with an impact face and a return face disposed in circumferentially spaced relation which when rotated in a first direction forcefully strikes its impact face on an impact face of a hammer member and the kinetic energy and rotational movement is transmitted in one direction to a member engaged with the hammer member.
A still further object of this invention is to provide a percussive rotational impact hammer assembly that is simple in construction, inexpensive to manufacture and rugged and reliable in operation.
Other objects of the invention will become apparent from time to time throughout the specification and claims as hereinafter related.
The above noted objects and other objects of the invention are accomplished by a percussive rotational impact hammer assembly for creating high torques wherein a generally cylindrical piston rotatably mounted on a hammer inside an outer casing oscillates on the hammer and strikes an impact surface on the hammer. The interior surface of the outer casing and exterior of the hammer form an annulus in which the piston rotatably oscillates and the piston divides the annulus into an impact-driving chamber and return chamber. The piston and hammer have pressurized fluid ports and passageways for conducting pressurized fluid to alternately pressurize the chambers to rotate the piston such that an impact face on the piston strikes an impact face on the hammer and the kinetic energy of the piston and the rotational movement is transmitted via the hammer to a member engaged with hammer, such as a drill bit or other member. The rotational impact hammer assembly can be adapted for use in a downhole hammer, in break out tongs for drill pipe, in wrenches for loosening or tightening nuts and bolts, or in other mechanical devices where high torque is desired. Another aspect of the invention is a downhole percussive hammer/drilling tool incorporating the rotational impact hammer assembly. Still another aspect of the invention is a wrench incorporating the rotational impact hammer assembly for loosening or tightening nuts and bolts or other threaded connections.